A typical example of zone-by-zone printing press control is ink or water feed control done on an incremental basis across the respective ink or water fountains. A press control console is usually provided for controlling ink or water feed and typically has an elongated array of ink control keys arranged in pairs (an increase and decrease key for each zone), and the key pairs are displaced across the control panel at a spacing related to the zone size established by the adjusters in the fountain. Thus, the zone size established by the adjusters in the fountain, and the keys on the control panel correspond to that spacing to allow the press operator the opportunity to mentally coordinate adjustments he is making on a zone-by-zone basis with the requirements or deficiencies in the sheet being printed. In electronic control systems, memories are usually provided for storing control information on a zone-by-zone basis. Such control information can include, for example, desired optical density information for each zone, actual optical density information for each zone, the ink fountain settings for each zone, and the like. In many systems, it is left to the operator, however, to mentally coordinate the electronically stored information, which is stored on a zone-by-zone basis, with the resulting printed image. The operator can attempt to coordinate the two by estimating zone positions on the printed sheet either mentally or by juxtaposing the sheet with the ink keys on the control panel.
Published German patent application No. DE-Al 3 325 006 discloses a display device for ink control system for printing presses wherein ink density values, adjustment and tolerance values, set values, and actual values are displayed on a display screen. The values to be displayed are either keyed in on an ink control panel, or detected by detectors disposed in ink zones on the press. Provision is made for scanning the actual image pattern from a hard copy image of the printed form, such as by means of a standard video camera. The video information is translated and stored for display on the same screen which displays the control information. Thus, the display screen not only displays the control information but also a superimposed image of the form being printed, so that the pressman can make a definite association between the displayed values of control information and the displayed superimposed image. Thus, deviations in the control parameters can be related to the actual image at a glance, and the operator has the opportunity to immediately make the necessary corrections. However, a primary disadvantage of this known apparatus is the need for an expensive recording device such as a video camera for scanning of the image, and the further complex electronics needed for converting the image into electronic signals compatible with the control system display, an image mixer for mixing the control information and the image information, and the necessary composite signal generator for superimposing both images on the same display screen.